Method of forming a high precision flexible abrasive member

ABSTRACT

A method of manufacturing a flexible abrasive member, includes the steps of providing a porous substrate, impregnating the substrate with an electrically isolating material, treating a side of the impregnated substrate so as to provide areas with different properties as to water or solvent resistance, washing the impregnating substrate with water or solvent so as to wash away the areas with relatively low water or solvent resistance for obtaining a prepared substrate with discrete areas, placing the prepared substrate in a metal deposition math, and depositing metal in the discrete areas in the presence of abrasive particles so as to form abrasive metal deposits.

The invention is related to the field of forming flexible abrasivemembers. Such members, which may take the form of circular pads forgrinding discs, or of loop shaped bands, are generally manufactured bydepositing metal on a substrate, in the presence of abrasive particles.These abrasive particles become embedded in the metal deposits, andprovide the abrasive action of the abrasive member.

The metal deposits, which support the abrasive particles, are usuallyadhered to a substrate in order to provide a strong bond. This bondshould be strong enough to withstand the high wear and tear which occursduring grinding.

From the state of the art, several methods are known for manufacturingsuch abrasive members. According to GB-A-1375571, a sheet is embedded ina backing material, leaving only isolated areas exposed on one side ofthe sheet. Subsequently, a metal together with embedded abrasiveparticles is deposited on these isolated areas by means of a platingprocess.

This prior art method has the disadvantage that, due to the fact thatthe isolated areas are only on one side of the sheet, the process ofdepositing the metal is rather slow. The isolated areas should beactivated by a metal activation bath, then be cleaned in a separatecleaning bath and be plated by electroplating. Apart from the slowprogress of this method, it is environmentally unfriendly having regardto the chemicals used in the activating and cleaning baths. Furthermore,the quality of the adhesion between metal deposits and the sheet isrelatively poor.

GB-A-1534448 teaches a method for manufacturing an abrasive member bymasking off a backing sheet with a mask such as a perforated tape,plastic, paint, photoresist rubber or the like, and by subsequentlydepositing a metal with abrasive particles on isolated exposed portionsof the backing sheet.

Also from EP-B-263785 a method of this kind is known. Both prior artmethods suffer from the problem that the metal deposits cannot be formedwithin a well defined boundary, in case the mask is applied on one sideof a porous substrate. In those cases, the non covered side of thesubstrate will be plated together with the isolated, exposed areas onthe other side. This results in a long production time, and also in aless flexible product.

The object of the invention is to provide a method for manufacturing aprecision flexible abrasive member which is both cheap and quick, andwhich provides a better adherence of the metal deposits onto thesubstrate. This object is achieved by a method of manufacturing aflexible abrasive member, comprising the steps of:

providing a porous substrate,

impregnating the substrate with an electrically isolating material,

treating a side of the impregnated substrate so as to provide areas withdifferent properties as to water or solvent resistance,

washing the impregnated substrate with water or a solvent so as to washaway the areas with a relatively low water or solvent resistance forobtaining a prepared substrate with discrete areas,

placing the prepared substrate in a metal deposition bath, and

depositing metal in said discrete areas in the presence of abrasiveparticles so as to form abrasive metal deposits.

By impregnating the substrate, it is fully and reliably covered on bothsides. This means that only in discrete areas from which subsequentlythe impregnating material is removed, the porous substrate isaccessible. The rest of the substrate is fully inaccessible, whichensures that metal deposition only takes place in very well defined,discrete areas.

As before, it is still possible to create open, discrete areas only onone side of the substrate. However, for obtaining a good adherence, itis preferred to create open areas on both sides of the substrate. Incase the discrete areas thus obtained on both sides of the substrate arecongruent, the substrate is embedded fully in the metal deposits, thusproviding a strong bond.

Alternatively, it is possible to treat the other side of the substratefully. In that case, said side is completely covered by the electricallyisolating material.

The treatment referred to before, by means of which discrete areas areobtained, can take several forms. Preferably, said treatment comprisesthe steps of:

impregnating the substrate with a resin, and

exposing the discrete areas to UV-light so as to render them water orsolvent resistant for forming a prepared substrate.

The discrete areas may be defined by the openings of a film placedbetween a source of UV-light and the side in question of the substrate.

The step of impregnating the substrate may be carried out in severalways as well. According to a first possibility, the substrate isimpregnated by dip coating. Separate pieces of substrate material aredipped in a container comprising a fluid coating material. Afterremoving and drying the coating, the substrate can be processed further.This method is in particular suitable for small batches.

Preferably, the porous substrate is electrically conductive, and themetal deposits are electro-formed.

FIG. 1 shows a step of dipcoating a substrate.

FIG. 2 shows the step of drying the impregnated substrates.

FIG. 3 shows the step of treating the substrate.

FIG. 4 shows the step of washing the substrate.

FIG. 5 shows the step of treating a substrate from both sides.

FIG. 6 shows a step of washing said substrate of FIG. 5.

FIG. 7 shows a first flexible abrasive member.

FIG. 8 shows a second flexible abrasive member.

According to the method of FIG. 1, porous substrate 1 is dipcoated in aresin bath 3. The thickness and the precision of the thickness of theresin coating 2 is controlled by precision doctor blades or squeegees 4.The product 5 thus obtained, comprising the porous substrate 1 oncefilled with the precise and controlled amount of resin 2 is ovendried,as shown in FIG. 2.

The next step is to expose discrete portions 9 of product 5 through afilm 6 with a specific pattern 7, of the ovendried resin to UV-light 8to render those exposed portions 9 water and solvent resistant: see FIG.3. The non exposed areas 10 will not become water-resistant and will bewashed away (FIG. 4) in a water stripping tank 11 which is moved bypressing air through a perforated tube 12 to accelerate the washingprocess. This method is working and is valid as long as very thinsubstrates are being used between 25 and 100 micron with at least 25%open areas. Thus, a prepared substrate 14 comprising open areas 13 isobtained.

Another aspect of the invention is to also be able to make an abrasiveaccording to the invention on substrates which are thicker than 100micron or less open than 25%. As explained before, any exposed parts ofthe substrate will plate independently from being masked or not as longas they are not fully covered by electrically isolating material as aresin for example. This means that in the case the porous substrate usedis thicker than 100 micron or less open than 25%, the UV-light will notbe able to fully penetrate the resin and to make it water and solventresistant. The result would be that the resin would be washed away atthe backside of the substrate and this uncovered area would be filledwith metal bond in the deposition process.

To avoid this problem the fully in resin imbedded porous substrate 5will be exposed (see FIG. 5) to UV-light 15 from both sides. On bothsides a film 16 with the desired pattern can be applied but at least toone side. This substrate is than freed (FIG. 6) from the areas of notwater-resistant resin in a water stripping tank and providing a preparedsubstrate 17 having open areas 18 on one side only.

Thanks to this process, a precision is achieved which was unknown inflexible super abrasive members using an open porous substrate. The sizeand quantities of the strands, parts or openings are not relevantanymore. The resin hardened with UV-light will stay exactly in thedesired place with the desired thickness as wanted.

Once the so prepared flexible porous substrate is dried, the metal bondis being electroformed within the discrete openings. An electroformingprocess has been elected instead of a classical electroplating techniqueused in the filled because it avoids the activating and cleaning processas mentioned in the state of the art. The metal bond is formed directlyin an on the strands, parts and openings of the flexible, poroussubstrate in the presence of abrasive in an electrodeposition bath,

As a result, an abrasive member 20 or 23 is obtained with metal deposits21 respectively 24, carrying abrasive particles 22. The abrasive member20 with throughgoing deposits 21 of FIG. 7 is obtained by carrying outthe deposition process on the prepared substrate 14 according to FIG. 4.The abrasive member 23 of FIG. 8 is obtained by carrying out thedeposition process on the prepared substrate 17 according to FIG. 6.

Even though the here described method is quite expensive when appliedwith small quantities the cost of manufacturing is unbeaten when a massproduction process is applied.

What is claimed is:
 1. Method of manufacturing a flexible abrasivemember, comprising the steps of: providing a porous substrate;impregnating the substrate with an electrically isolating material;treating a side of the impregnated substrate so as to provide areas withdifferent properties as to water or solvent resistance; washing theimpregnated substrate with water or a solvent so as to wash away theareas with a relatively low water or solvent resistance for obtaining aprepared substance with discrete areas, said discrete areas being saidareas having the electrically isolating material removed; placing theprepared substrate in a metal deposition bath; and depositing metal insaid discrete areas in the presence of abrasive particles so as to formabrasive metal deposits.
 2. Method according to claim 1, wherein bothsides of the substrate are treated.
 3. Method according to claim 2,wherein the discrete areas of both sides are congruent.
 4. Methodaccording to claim 1, wherein the other side of the substrate is fullytreated.
 5. Method according to claim 1, comprising, the steps of:impregnating the substrate with a resin, and exposing the discrete areasto UV-light so as to render them water or solvent resistant for forminga prepared substrate.
 6. Method according to claim 5, wherein thediscrete areas are defined by the openings of a film placed between asource of UV-light and the side of the substrate.
 7. Method according toclaim 1, wherein the substrate is impregnated by dip coating.